1. Field of the Invention
The present invention is related to a filament placement system having a head for applying filaments to a mandrel for forming tubular articles.
2. Description of Background and Other Information
In present filament winding systems, fibrous rovings or tows, impregnated with a thermosetting resin, are wound in a helical pattern in a number of superimposed layers onto a mandrel to produce a tubular article. In most types of filament winding operations, the rovings pass through a delivery eye or from a delivery roller across an air space onto the part. In such systems, tows cannot be added or deleted during operation to adjust to the varying contours of the part being wound. Furthermore, such systems are limited to geodesic or natural path fiber patterns. Conventional tape laying systems generally provide positioning of the rovings on flat or slightly contoured surfaces. However, these systems cannot wind three dimensional contours without fiber gaps or overlaps, unless an impracticably narrow band is employed. Tape layers cannot vary the band width without terminating the entire band.
The inability to alter bandwidth while winding parts with non-uniform cross-section, such as fuselages, tapered wing skins, domes or missile nose cones, results in overlapping or gapping of the winding band. The inability to accurately place fiber at the optimum angle results in heavier than necessary designs. In some cases, this results in a design that cannot be automated and provides no cost or weight savings compared to a corresponding metal part.
Co-pending application Ser. No. 07/275,313, filed Nov. 23, 1988, now U.S. Pat. No. 5,045,147 discloses a fiber placement system that overcomes many of the disadvantages of filament winding systems. The system disclosed therein is capable of selecting any or all of thirty-two available tows and terminating and adding them on the mandrel tooling upon computer command. This system allows for the band width to be automatically varied between one and thirty-two tows, and also allows for a full band termination and restart.
A limitation of this design has been encountered due to the cable actuation system utilized for the cutting and adding device. The actuation system of this design consists of remotely located pneumatic cylinders linked to flexible cables which transmit the mechanical force to the delivery head. This cable system has been found to restrict the actuation speed, which can be critical particularly in the cutter mechanism. The presence of the cable system also makes delivery head change-out slow and difficult.
A more desirable delivery head would have an actuation method that would facilitate head installation and removal and, at the same time, providing faster actuation speeds. The delivery head would also be easy to disassemble and clean, thereby reducing down-time.
An additional limitation of the known design has been found to be fiber buildup at the groove openings of the guide trays. In the known design, there had been sharp corners that would tend to catch the tows and cause buildup.